Radar Sensing using Dual-Beam Reconfigurable Intelligent Surface

TL;DR

This work investigates radar sensing with reconfigurable intelligent surfaces (RIS), focusing on a dual-beam RIS realized through one-bit phase quantization. The authors develop a 2D RIS radar model, derive the generalized Snell law, and compare ideal single-beam tuning with a practical dual-beam (1-bit) implementation, benchmarking against a metal plate. They show that RIS enables directed, non-specular backscatter, enhancing forward and reverse RCS in off-specular regions, with dual-beam RIS offering broader angular coverage at the cost of lower on-axis RCS due to power splitting and hardware losses. Experimental measurements at 5.5 GHz validate the simulations, demonstrating a ~1° beam-squint and confirming the practical trade-offs between beam steering accuracy, RCS, and reciprocity, while highlighting the potential for RIS-enabled around-the-c corner radar in multi-target scenarios.

Abstract

Around-the-corner radar sensing offers an opportunity for the radar to exploit multipath scattering along walls to detect targets beyond blockages. However, the radar detection performance is limited to spotting uncooperative targets at specular angles. Recently, reconfigurable intelligent surfaces (RIS) involving metasurfaces with tunable unit cells have been researched for enhancing radar coverage around corners by directing beams towards non-specular angles. This article examines how practical considerations regarding the phase tuning of unit cells impact the RIS performance. Specifically, we examine the radar cross-section (RCS) obtained from two RIS configurations: In the first, each atom of the RIS is tuned based on a theoretical analog phase shift to realize idealized one-beam patterns at the desired angles. In the second configuration, each atom of the RIS is tuned based on a low-complexity, one-bit quantized element phase shift, which results in dual symmetric beams. The RIS configurations are then benchmarked with a metal plate of similar dimensions in both simulations and measurements.

Figures (5)

• Figure 1: Illustration of RIS-based Radar system for target detection.
• Figure 2: Simulation setup for Radar, RIS, and multiple targets.
• Figure 3: (a) Metal, (b) One-beam, (c) Dual-beam RIS with incident angles of (i) $-15^\circ$, (ii) $-30^\circ$, (iii) $-45^\circ$, and (iv) $-60^\circ$ respectively.
• Figure 4: Spectrograms of targets for (a) Metal, (b) One-beam RIS, and (c) dual-beam RIS .
• Figure 5: (a) Experimental setup for beam-steering using RIS, (b) close-up view of RIS, and (c) close-up view of receiver setup.